Environmental Influence on Utilization of Energy in Swine Diets

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Abstract
Two-hundred-fifty-six Yorkshire weanling pigs were used in four trials conducted to compare the effects of summer and winter seasons (warm and cool), dietary energy (1.5 and 9.0% added animal fat) and protein sources on performance and carcass characteristics of growing-finishing swine. Average daily gains were not affected significantly by dietary energy level with combined data from warm and cool-season trials. Nine percent fat supplementation to the ration resulted in a 3% improved feed efficiency (P<.05), slightly increased dressing percent and backfat and decreased loin-eye area and percent primal cuts (P<05). Seasons had no significant effect on growth rate, feed efficiency or dressing percent with combined dietary treatment data. Pigs fed during winter had carcasses with a significantly (P<.05) higher percent of ham, loin and lean cuts. There were important season-energy interactions. Daily gains were identical (.75 kg) for dietary fat levels during cool-season trials; while during summer trials pigs fed high fat diets gained .05 kg faster than pigs fed low fat diets. This difference resulted in a significant interaction at the 10% level between fat level (9.0%) and season for rate of gain. Feed efficiency was improved by 13.0% as the level of energy was increased during the summer (P<.05). Utilization of calories for growth was estimated to be equal for low and high energy diets during cool season trials, whereas high energy diets were most efficient in warm season trials. In summer, pigs fed 9% fat yielded carcasses with higher dressing percent, more backfat (P<.01), and less loin-eye area and lean cuts (P<.05). Protein source did not significantly affect growth rate, feed efficiency, dressing percent or backfat thickness. Means of other carcass traits differed (P<.05) among some dietary treatments. Barrows gained faster and had more (P<.01) backfat than gilts, but gilt carcasses were longer (P<.01), with a larger (P<.01) loin-eye area and a higher (P<.05) yield of lean cuts than barrows. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.